Mounting WebDAV (Web Distributed Authoring and Versioning)Web Distributed Authoring and Versioning (WebDAV) serversgreenbytes GmbHHafenweg 16MuensterNW48155Germany+49 251 2807760+49 251 2807761julian.reschke@greenbytes.dehttp://greenbytes.de/tech/webdav/
In current Web browsers, there is no uniform way to specify that a user
clicking on a link will be presented with an editable view of a WebDAV
server. For example, it is frequently desirable to be able to click
on a link, and have this link open a window that can handle drag and
drop interaction with the resources of a WebDAV server.
This document specifies a mechanism and a document format that enables
Web Distributed Authoring and Versioning (WebDAV) servers to send
"mounting" information to a WebDAV client. The
mechanism is designed to work on any platform and with any combination
of browser and WebDAV client, relying solely on the well-understood
dispatch of documents through their MIME type.
Please send comments to the Distributed Authoring and Versioning (WebDAV)
working group at , which may
be joined by sending a message with subject "subscribe" to
. Discussions of the
WEBDAV working group are archived at
.
Note that although discussion takes place on the WebDAV working
group's mailing list, this is not a working group document.
XML versions, latest edits and the issues list for this document
are available from .
Umbrella issue for editorial fixes/enhancements.
Update MIME registration to RFC4288 form.
By definition, a WebDAV server () is an HTTP
server as well (). Most WebDAV servers can be
(at least partly) operated from an HTML-based user interface in a web browser. However,
it is frequently desirable to be able to switch from an HTML-based view to
a presentation provided by a native WebDAV client, directly supporting
the authoring features defined in WebDAV and related specifications.
This document specifies a platform neutral mechanism based on the dispatch
of documents through their MIME type. For completeness, lists other
approaches that have been implemented in existing clients.
For example, many educational institutions use WebDAV servers as a mechanism
for sharing documents among students. Each student owns a separate collection
structure on a WebDAV server, often called his/her "locker". Ideally, when
users click on a link in an HTML page provided by the university (perhaps
by their university Web portal), an editable view of their locker will appear.
The terminology used here follows that in the WebDAV Distributed
Authoring Protocol specification .
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD",
"SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be
interpreted as described in .
This document uses XML DTD fragments
() as a purely notational convention. In particular:
Element names use the namespace "http://purl.org/NET/webdav/mount". When
an XML element type in this namespace is referenced in this document outside
of the context of an XML fragment, the string "dm:" will be prefixed to the element name.
Element ordering is irrelevant.Extension elements/attributes (elements/attributes not already defined
as valid child elements) may be added anywhere, except when explicitly
stated otherwise.
A WebDAV mount request is encoded in a specific XML format ()
with a well-defined MIME type (see ).
The MIME type allows user agents to dispatch the content to a handler
specific to the system's WebDAV client.
The elements defined below use the namespace "http://purl.org/NET/webdav/mount".
<!ELEMENT mount (url, open?, username?) >
<!ELEMENT url (#PCDATA) >
<!-- PCDATA value: scheme ":" hier-part, as defined in section 3 of
-->
<!ELEMENT open (#PCDATA) >
<!-- PCDATA value: path, as defined in section 3 of
-->
<!ELEMENT username (#PCDATA) >
The <dm:mount> element acts as container for all the remaining elements
defined by this protocol.
The mandatory <dm:url> element provides the HTTP URL of the WebDAV collection
that should be mounted by the client.
The optional <dm:open> element instructs the client to display the specified
child collection; its URL is computed by concatenating this element's
value with the URL obtained from the <dm:url> element
(see for a discussion about
why this element only supports displaying collections rather than opening
arbitrary documents).
The server can use the optional <dm:username> element to specify the name
of the currently authenticated principal. A client can use this value to select
a matching mount point (different users may have mounted the URL with
different credentials under different local mount points) or to provide
a meaningful default for
authentication against the server. It is common that browser and
WebDAV client do not share HTTP connections, so including this information
in the mount document increases usability.
Implementation Note: If a <dm:username> element is present, public
caching of the document should be disallowed. Thus, appropriate 'Vary' or
'Cache-Control' headers are needed in the server response.
In the example below, the client first retrieves a representation of a
WebDAV collection using a generic Web browser (1). The returned HTML content
contains a hyperlink that identifies the "davmount" document
in the format defined in (2). The user follows this
link (3), which causes the server to return the "davmount" document to the user's
browser (4). The browser in turn passes the content to the application that
was registered to handle the "application/davmount+xml" MIME type, usually
the default WebDAV client on the client's system.
(1) Client retrieves representation of WebDAV collection "/user42/inbox/".
GET /user42/inbox/ HTTP/1.1
Host: www.example.com
(2) Server returns representation.
HTTP/1.1 200 OK
Content-Type: text/html
Content-Length: xxx
..
<a href="?action=davmount">View this collection in your
WebDAV client</a>
..(note that the example shows only that part of the HTML page
that contains the relevant link)
(3) Client follows link to "davmount" document
GET /user42/inbox/?action=davmount HTTP/1.1
Host: www.example.com
(4) Server returns "davmount" document
HTTP/1.1 200 OK
Content-Type: application/davmount+xml
Content-Length: xxx
Cache-Control: private
<dm:mount xmlns:dm="http://purl.org/NET/webdav/mount">
<dm:url>http://www.example.com/user42/</dm:url>
<dm:open>inbox/</dm:open>
</dm:mount>
This document does not introduce any new internationalization considerations
beyond those discussed in , Section 16.
MIME media type nameType name:
applicationMIME subtype nameSubtype name:
davmount+xmlMandatory parametersRequired parameters:
none
Optional parameters:
"charset":
This parameter has identical semantics to the charset parameter of
the "application/xml" media type as specified in .
Encoding considerations:
Identical to those of "application/xml" as described in , section 3.2.
Security considerations:
As defined in this specification.
In addition, as this media type uses the "+xml" convention, it shares the same security considerations as described in , section 10.
Interoperability considerations:
There are no known interoperability issues.
Published specification:
This specification.
Applications that use this media type:
SAP Netweaver Knowledge Management, Xythos Drive.
Additional information:
Magic number(s):
As specified for "application/xml" in , section 3.2.File extensionFile extension(s):
.davmount
Fragment identifiers:
As specified for "application/xml" in , section 5.
Base URI:
As specified in , section 6.Macintosh File Type codeMacintosh file type code(s):
TEXT
Person and& email address to contact for further information:
Julian Reschke <julian.reschke@greenbytes.de>
Intended usage:
COMMON
Restrictions on usage:
None.
Author:
Julian ReschkeAuthor/Change controller:
IESG
All security considerations connected to HTTP/WebDAV and XML apply for
this specification as well, namely (Section 17)
and (Section 7).
In addition, client implementers must be careful when implementing the
<dm:open> element (see ). It MUST NOT
be used to initiate any action beyond displaying the contents of a
WebDAV collection (supporting
"opening" documents could be abused to trick a user into letting the operating
system's shell execute arbitrary content, possibly running it as an
executable program).
This draft has benefited from thoughtful discussion by Emile Baizel,
Spencer Dawkins, Stefan Eissing,
Joe Gregorio, Michal Gregr, Jim Luther, Jaroslav Mazanec, and Jim Whitehead.
Key words for use in RFCs to Indicate Requirement LevelsHarvard Universitysob@harvard.eduHTTP Extensions for Distributed Authoring -- WEBDAVMicrosoft Corporationyarong@microsoft.comDept. Of Information and Computer Science, University of California, Irvineejw@ics.uci.eduNetscapeasad@netscape.comNovellsrcarter@novell.comNovelldcjensen@novell.comHypertext Transfer Protocol -- HTTP/1.1University of California, Irvinefielding@ics.uci.eduW3Cjg@w3.orgCompaq Computer Corporationmogul@wrl.dec.comMIT Laboratory for Computer Sciencefrystyk@w3.orgXerox Corporationmasinter@parc.xerox.comMicrosoft Corporationpaulle@microsoft.comW3Ctimbl@w3.orgXML Media TypesIBM Tokyo Research Laboratorymmurata@trl.ibm.co.jpsimonstl.comsimonstl@simonstl.comSkymoon Venturesdan@dankohn.comExtensible Markup Language (XML) 1.0 (Third Edition)Textuality and Netscapetbray@textuality.comMicrosoftjeanpa@microsoft.comUniversity of Illinois at Chicago and Text Encoding Initiativecmsmcq@uic.eduSun Microsystemseve.maler@east.sun.comfrancois@yergeau.comUniform Resource Identifier (URI): Generic SyntaxWorld Wide Web Consortiumtimbl@w3.orgDay Softwarefielding@gbiv.comAdobe Systems IncorporatedLMM@acm.org
Guidelines for the Use of Extensible Markup Language (XML) within IETF ProtocolsVeriSign, Inc.21345 Ridgetop CircleDullesVA20166-6503US+1 703 948 3257shollenbeck@verisign.comDover Beach Consulting, Inc.POB 255268SacramentoCA95865-5268US+1 916 483 8878mrose@dbc.mtview.ca.usAdobe Systems IncorporatedMail Stop W14345 Park Ave.San JoseCA95110US+1 408 536 3024LMM@acm.orghttp://larry.masinter.netArchitecture of the World Wide Web, Volume OneSun Microsystems, Inc.W3Chttp://www.w3.org/People/Jacobs
Microsoft Internet Explorer implements a CSS extension that allows
switching to its own WebDAV client ("Webfolder", see
). However, at the time
of this writing this extension was not implemented by any other
user agent.
The "kio" library of the "K Desktop Enviroment" () uses
the URI scheme "webdav" to dispatch to the system's WebDAV client. This URI scheme
is not registered, nor supported on other platforms. Furthermore,
W3C's "Architecture of the World Wide Web, Volume One"
explicitly advises against defining new schemes when existing schemes can be
used:

A specification SHOULD reuse an existing URI scheme (rather than create a new one)
when it provides the desired properties of identifiers and their relation to resources.